N123-138 Series Snap Trac Dither Generator and ... - Moog Inc

SPECIFICATIONS
Dither Generator
Square wave at terminal 2.
Triangular wave at terminal 6.
Frequency ≈ 400 Hz.
Frequency range of 0.05 to 1000 Hz
can be obtained by changing R9
and/or C3 (20KΩ to 10MΩ and
0.01µF to 5µF).
freq =
1 ( –––––––) Hz
4•R9•C3
Amplitude ≈ 16 volts peak-to-peak
(each waveform).
See servovalve catalog for
recommended dither amplitude and
frequency.
The N123-138 Snap Trac Dither Generator and General Purpose Amplifier
contains a signal generator that supplies square and triangular waveforms that
may be used for dither in an electrohydraulic servosystem. Dither is typically
used to reduce system threshold caused by actuator and/or servovalve
friction.The general purpose amplifier may be used for low level amplification
of a signal, or may be custom modified if desired.
SPECIFICATIONS
Servoamplifier or general purpose
amplifier may be used for amplitude
adjustment.
Minimum load resistance: 20KΩ on
terminal 2; 5KΩ on terminal 6.
Temperature Range:
-20°C to 50°C (-4°F to122°F)
Power Required:
±15.0 VDC at ±17mA, regulated,
3-wire (±E) at terminals 7, 8, and 9.
This power is available from Model
N121-132 Snap Trac Servocontroller.
Amplifier
Inputs:
Two individual inputs at terminals 10 and 11; or differential input
between terminals 10 and 11.
Input signals may range from ±0.1 VDC to 100 VDC.
Output:
Output at terminal 12.
Load impedance ≥ 5 KΩ. ±10 VDC maximum output.
Gain:
General expression for amplifier gain with R16 = R18, R15 = R17,
J6 = R19 = Jumper and R25 full CW:
R24 + R25 e12 = (e11 - e10) (R16 / R15) ( 1+ –––––––––)
R23 DIMENSIONS
3.25 in width x 4.70 in length
Maximum Component Height: 0.69 in
1 2 3 4 5 6 7 8 9 10 11 12 13 14
N123-138 Series
Snap Trac Dither Generator
and General Purpose Amplifier
TP1
R7
R30
EXT EXT
P1
PIN14
INT INT
PIN13
J1
J2
J3
TP2
C1
C2
R6
R4
R5
R8
R10
R9
R11
R17
R15
R16
R29
COMMON
TP3
C4
R19
MODEL:N123-138
SN:
TP8
A1
D1
D2
R12
R13
R18
A2
R20
TP12
C3
CW R25
FEATURES
Construction
➢ Plug-in connectors for quick installation of board.
➢ Test points on all critical signals.
➢ Component standoffs on all user-configurable components.
➢ Twenty-turn potentiometers for all adjustable controls.
➢ Rugged construction with solder mask.
R28
R2
R1
R14
R27
R22
R24
R26
R23
R21
TP6
R3
GAIN

N123-138 DITHER GENERATOR AND GENERAL PURPOSE AMPLIFIER
INPUT SIGNAL
0 TO +15.0 VDC
SIGNAL GROUND
SEE NOTE 5
UNUSED INPUT
INPUT SIGNAL
0 TO -15.O VDC
SINGLE
INPUT SIGNAL
INDIVIDUAL INPUTS OR
DIFFERENTIAL INPUT
CIRCUITRY
Dither Generator
The dither generator consists of a
comparator stage (A1A), amplitude
limiting stages (A1C/D2 and A1D/D1)
and an integrating amplifier stage
(A1B). Upon startup,A1A will attempt
to go to + or - saturation. However,
the peak voltage will be limited to
approximately ±8 VDC by D1/A1D or
D2/A1C.A1B ramps up or down, as
the case may be, until the output
voltage is sufficient to cause the
feedback voltage at the comparator
(through voltage divider R8, R11) to
change polarity.At this point,A1A
switches polarity and A1B begins to
ramp in the opposite direction.
+E
7
5
R2
R1
NF
CW
R3
+E
+AMPLITUDE LIMIT
SIGNAL GROUND
C1
10uF
C2
10uF
TP8
8
POWER
INPUTS
(REGULATED)
49.9K
49.9K
POWER
INPUTS
-E
9
TP3
+E
(REGULATED)
TP2
3
J2 INT
EXT
12 4
13
A1D
14
TL084CN
11
-E
D1
2
SQUARE
WAVE
OUTPUT
SIGNAL
5
COMPARATOR
R6
TYPICAL STANDOFF
INTEGRATOR
NF
C3
-E
0.01uF
TP6
4 X
R30
0
R4
24.9K
R5
100K
2
3
11
A1A
1
TL084CN
4
+E
R7
2K
R8
49.9K
R9
61.9K R10
49.9K
6
5
-E
11
7
A1B
TL084CN
4
+E
R11
49.9K
6
TRIANGULAR WAVE
OUTPUT SIGNAL
-E
1
J1
EXT
INT
TP1
9 11
8
10 A1C
TL084CN
4
D2
GENERAL PURPOSE AMP
+E -AMPLITUDE LIMIT
R21
R22
R12
R13
10K
NF
(TEST POINT)
TP12
49.9K 49.9K
6
R19 5
5
R14 CW
NF
-E
+E
0
R20
NF
7
6 A2B
TL082CP
12
GAIN
13
R27
NF
6 R26
NF
R24
10K
R25
CW
100K
11
R15
100K
DIFFERENTIAL AMP
R16
100K
+E
R28
0
TL082CP
CW
-E
BIAS
R23
10K
6
OUTPUT SIGNAL
10
R17
100K
3
2
8
A2A
4
R29
0
R18 -E
1
J3
PIN 13
PIN 14
14
100K
NOTES:
C4
NF
1. NF = NOT FURNISHED
2. ■ = PIN 1 (SQUARE PIN)
3. = INDICATES COMPONENT MOUNTED ON STANDOFFS
4. CW = CLOCKWISE
General Purpose Amplifier
A differential input amplifier (A2A)
and a non-inverting amplifier (A2B)
are mounted on this board for
general signal amplification. Input
signals are applied to terminal 10
and 11, with the output signal at
terminal 12.Amplification of each
stage should be between 0.1 and 10
volts/volt with resistor values between
10KΩ and 100 KΩ.
SPECIAL MODIFICATIONS / SET-UP / OPTIONS
Refer to section on set-up instructions and technical information for additional
assistance on card usage and application. R1, R14, R27, R26, R24, R19 sizing
options are located in set-up instruction section of literature.
5 DO NOT CONNECT DC SIGNAL TO PIN-4. REFER TO SET-UP
INSTRUCTION SECTION FOR ADDITIONAL INFORMATION.
6 REFER TO “SPECIAL MODIFICATION” OPTIONS
ADJUSTMENTS
Gain (R25) – provides 12:2
amplification range of A2B.
Bias (R27) – not furnished.
(Recommended size is 100K)
MOUNTING:
Mount using Curtiss type TR-3
plastic track (Moog P/N 65419-1)

SET-UP INSTRUCTIONS
The card is factory built to supply a
Dither Frequency of Approx. 400Hz
Calculated Outputs
➢Determine required Dither
frequency needed
➢Calculate Dither Frequency ➡
f DITHER = [1 / (4xR9xC3)]Hz (using
Triangle waveform)
➢Refer to Servovalve Catalog for
recommended dither amplitude &
frequency; Consult factory as
required
➢Use Square Waveform for most
valve applications
➢Steady State Triangular Waveform
output at Pin-6:
E6 = (R5 / R4 + R5) E4
Vdc (Error Correction)
➢Slope of Output:
Slope = (-E2 / R9 x C3)
Volts/Sec
Pos Slope Rate = +12V/msec
Neg Slope Rate = -12V/msec
Preliminary Test Set-Up
➢R25 full CCW
➢Set Jumpers J1 & J2 to INT
(Internal) position
➢Set J3 to PIN-13 position
EXT (External) Control of Ramp
Rate
➢For + Slope, J1 = EXT
➢Rate controlled by input signal at
Pin-1 (0 to -15V)
➢For - Slope, J1 = EXT
➢Rate controlled by input signal at
Pin-1 (0 to +15V)
Frequency Test Set-Up
➢Verify Dither Frequency signal at
TP2 is 400±40 Hz
➢Verify factory set Amplitude at TP2
is 16Vp-p
For Slope or Ramp Adjust
Capability over 12:2 range
➢Install a 100K pot in the R1 & R14
position
➢Remove R2, R3, R12 & R13 (49.9K)
resistors
➢Adjusting R1 will increase the Neg
Slope of the waveform
➢Adjusting R14 will increase the Pos
Slope of the waveform
➢Offset Voltage may be provided by
R1 & R14 which will result in unsymmetrical
waveforms
Setting the (+) Amplitude Limit
➢R2 & R3 (49.9K) resistors provides
a balanced positive voltage divider
(+15V)
➢This along with D1 / A1D limits the
Pos. Peak voltage to +8Vdc
(Approx. 1/2 of +15V)
Setting the (-) Amplitude Limit
➢R12 & R13 (49.9K) resistors
provide a balanced negative voltage
divider (-15V)
➢This along with D2 / A1C limits the
Neg Peak voltage to -8Vdc
(Approx. 1/2 of -15V)
General Purpose Amplifier
➢The General Purpose Amplifier can
be used for Dither Amplitude
Adjustment using R25 of A2B
Non-Inverting Stage ➡ provides
12:2 amplification range
➢Auxiliary Non-Inverting Amplifier
(A2B): Gain Equation
Av = Gain = e12 / e13 =
[ 1 + (R24 + R25) / R23 ]
➢A differential input Amp (A2A) & a
Non-Inverting Amp (A2B) are
supplied for general signal
amplification
➢J3 provides jumper select options
to “combine” or “isolate” stages
A2A & A2B
➢Input signals are applied to
Differential Pin-10 & Pin-11 with
output signal at Pin-12
OR
➢Connect Pin-2 (Sq Wave output) or
Pin-6 (Triangle Wave output) to
Pin-13 (Single Input Signal) for
Amplitude Adjust using R25 with
output signal at Pin-12
➢With Input applied to Pin-11 and
Pin-10 grounded, a positive output
will result
➢Adjust R25 for 12:2 ratio
amplification ➡ ±10Vdc max
output is possible
➢Zero Offset pot (R27) may be
installed for Bias control of signal;
Set R27 to 100K Pot and R26 to
100K / 1% resistor
➢Set Gain Pot R25 (Amplitude Adj)
full CCW for min Gain / full CW
for max Gain
Special Modification Information / Options
➢Comparator Stage (A1A)
Configured as a ‘Square-Wave’ Generator providing a 400Hz
Square Wave output signal at Pin-2.A ‘Triangular-Wave’ output
signal at Pin-6 is provided via use of Integrator Stage (A1B) with
frequency dependent on selection of R9 & C3.
➢No Input Signal is required at Pin-4 with R30 connected to
ground via 0Ω jumper
➢R9 & C3 are installed at factory to provide a fixed 400Hz frequency
at approximately 16VP-P amplitude.Amplitude may be varied by
using General Purpose Amplifier Stage.
➢Other frequencies from 0.05Hz to 1KHz are available by changing
R9 & C3
General Purpose Amplifier (A2B)
➢Gain ➡ eo / ein = [1 + (R24 + R25 / R23 ]
➢Configured as a ‘Non-Inverting’ Amplifier for general signal
amplification with optional NF component selection / sizing & reconfiguration
options
➢Input Amplification resulting in Output Voltage >10Vdc are limited by
Saturation
➢R25 provides 12:2 amplification range of A2B
➢R19 may be adjusted to obtain Custom Signal Scaling (See
Application Example)
➢R24 may be adjusted to obtain a different amplification range
including:
R24 Min Gain
Examples
Max Gain Max Output @ Pin-12
0Ωjumper 1 11 ±10Vdc
1K 0.1 11.1 ±10Vdc
Example: Custom Signal Scaling Application using Aux Amp
➢Scaling ±8Vdc Input Square Wave ➡ ±1Vdc at Output Pin-12
➢Refer to Fig.A
e 13
R19
0Ω
VREF
R23
10K
R21
10K
Fig A - General Purpose Amp Configuration
+
-
R24
10K
A2B
R25 cw
100K
Jumper
e 12

SET-UP INSTRUCTIONS
➢Determine V REF needed to reduce +8v to +1v
➢Calculate resistor value R19
➢Jumper R24 (This changes Gain Ratio from 12:2 to 11:1)
➢Remove R19 (0Ω) & replace with 70K, 1% resistor
➢Set R25 Pot full CCW for ‘Min’ Gain of ‘1’
➢Verify +1Vdc Output at Pin-12
Calculations
➢@1Vdc = V REF ➡ V REF = +e 13 [R21 / (R21 + R19)]
➢Solve for R19 ➡ R19 = 70K
➢Calculate Gain ➡ e 12 / e 13 = [1 + (R24 + R25) / R23]
➢With R24 = 0 ➡ Min Gain = 1 @ R25 full CCW
➡ Max Gain = 11 @ R25 full CW
➢Resultant Output ➡ +1Vdc Output @ Pin-12 @
+8Vdc Input
CLOSED LOOP POSITION CONTROL
MODEL N121-132A
SERVOCONTROLLER
(Snap-Trac Card)
A1A
R8
SCALE
MODEL N123-138
DITHER GENERATOR
(Snap-Trac Card)
DITHER FREQ WAVEFORM
A1A
R8
LOOP GAIN-1
R9
R11
A1B A2B
A1B
Note: Consult Moog Servovalve Catalog for recommended
dither Amplitude & Frequency. Select 'waveform' as per
requirements of application and actual desired response.
C3
R46
+E
-E
-E
+E
26
27
28
29
22
18
3
12
13
19
17
21
10
2
2
6
7
9
8
115 VAC
50-60 Hz
Position Servo with Dither Generator Application
-15V
+15V
+15V
-15V
Ps
C2 C1
ACTUATOR
POSITION COMMAND
SERVOVALVE
R
Questions & Answers
Question: Can the Dither Frequency
be set-up for either a ‘square wave’ or
‘triangular wave’?
Answer: The valve is usually run with
the square wave output signal but will
depend on the actual desired response.
Square wave will provide a more
abrupt control from hard over position
whereas the Triangular wave will
provide a softer control response. It
will depend on valve ‘friction’ or
‘sticking’ action caused by actuator or
servovalve response. Research indicates
that the type of waveform, whether
sine, square or triangular shape, will not
significantly effect the valve
performance. It is strictly related to
required frequency & amplitude for the
specified valve hardware.
Question: Does the type of
servovalve used determine the
frequency & amplitude?
Answer: The card is factory set for
400Hz frequency with an amplitude of
16Vp-p.The Moog Servovalve Catalog
should be consulted for recommended
dither amplitude & frequency. If a
competitors valve is used, consult the
appropriate Factory as required.The
actual frequency / amplitude will also
be determined on the system set-up.
Fine tuning may need to be applied to
reach satisfactory results.As an
example, a 760 Series valve may require
a dither frequency of approximately
400Hz at a current amplitude of 10mA
peak-to-peak (series coil configuration).
Caution is advised since the use of
higher dither frequency other than
specified, can excite internal valve
resonance which may lead to valve
failure or degrade the valve life. Proper
FORCE
ON
LOAD
POSITION FEEDBACK
amplitude (% of valve current) should
also be stressed so as not to exceed
20% of rated current.
Question: What purpose do the NF
(non-furnished) components provide in
the circuit such as pots R1, R14 and
R27? What are the recommended
component sizes for setting up these
feature adjustments?
Answer: Installation of R1 provides
adjustment of the ‘negative’ slope or
ramp rate over a 12:1 ratio. R14
provides adjustment of the ‘positive’
slope or ramp rate over a 12:1 range.
Recommended size is 100K for each.
The voltage divider resistors must be
removed for this feature to operate.
(Remove R2, 3, 12 & 13)
Question: What is the purpose of
the Auxiliary general purpose amp?
Answer: This stage is used for Dither
Amplitude Adj using R25 (Gain) pot of
A2B Non-Inverting Stage. Connect
Output Pin-2 (Sq Wave) or Pin-6
(Triangle Wave) to Pin-13 (Single Input
Signal) for amplitude adjustment using
R25 for a 12:2 ratio amplification.A
Zero Offset pot (R27) may be installed
for ‘Bias’ signal control. Set R27 to
100K Pot & R26 to 100K / 1% resistor.
Question: How much Dither should
be applied?
Answer: If external dither is applied
to Pin-1 or Pin-3, typically adjust for
±10% of valve rated current. J1 & J2
MUST be in the appropriate position.
This follows true for Internal dither.
Internal dither ±Slope is adjusted by
pots R1 & R14 (customer installed).
Dither current thru a servovalve
should NOT exceed 20% of rated
current.
Industrial Controls Division
Moog Inc., East Aurora, NY 14052-0018
Telephone: 716/655-3000
Fax: 716/655-1803
Toll Free: 1-800-272-MOOG
CDL6173 Rev B 500-199 1198